point of order: neither in law/politics (where the term is used) or in the description of a mechanical device, such as in a patent application (where the term is used) would i consider this to fall under the definition of "active operating mechanism". but i might be wrong and if i am then, fine, i'm about to learn something. (and to be clear, it's not the "operating mechanism" part i question, it's the term "active".)

metal and carbon are in contact with each other a lot, and on several parts of the bike. when a BB or headset bearings or dropouts or fork ends, or stems or compression rings attach to a carbon frame, it's metal against carbon in a way that absolutely is subject to stress (and therefore to testing). you used the term "impact" and, yes, that adds an additional element. but when i read the term "active operating mechanism" the way that term is typically used, when i've come across it, it's in the regular or prime function of the device or motor or unit. a prime action that makes it do its thing. for example, a chain hanger wouldn't be considered the "active operating mechanism" of the bicycle's drive train.

over the life of the bike the manufacturer could hope that such contact is never made. however, it's clear that such contact is contemplated, or else the bike wouldn't have been built as it was. i'm not saying this is the ideal way to limit the radius of travel. (personally, i've never liked having these devices in the bikes i own.) my only point here is to question whether "active operating mechanism" is the appropriate term of art in this case, and it's not a minor point, because the repetitive, hard, banging of these two surfaces is not the intended use of the product, it is a rare circumstance of bike ownership.

---

Dan Empfield
aka Slowman

     
For what it's worth I'm a project engineer and senior engineering manager at a large aerospace and defense contractor. I've been in aerospace for 18 of my 26 years as an engineer. As such, I have ultimate technical responsibility for the design, manufacture, and certification for whole aircraft, avionics, and systems modifications. During my career I've been involve in a few crash investigations and detailed system operation and failure analyses to attribute the causes and reconstruct the events resulting in loss of crew SA (situational awareness) which resulted in a set of erroneous actions and ultimately deaths.

There are numerous factual errors in your description of the mcas system operation, and sensors. Number one on the list is that the primary sensor failure was an angle of attack (AoA) sensor... Not airspeed (pitot tube). However there are numerous other design and systems engineering, safety, and airworthiness errors involved. There are a whole host of errors in the failures and plenty of blame to go around. No major aircraft disaster in the last 50 years can be described by any one simple system failure. EVERY one is a complex set of circumstances and failures that results on a loss of crew control.

It is the complexity of the failures that has kept the fleet grounded. A simple problem such as a single point of failure would be easily rectified and the aircraft would already have returned to service.

Further your characterization of the division in responsibility between systems, and design engineer is simplistic... At best. As noted above, there are a lot of disciplines involved in the failure... Some are design, some are systems, some are safety, some are test, some are airworthiness, some are senior management (up the the ceo), and some are directly related the the FAA. Any description that simply attributes these failures to any single disciple is frankly wrong... And belies a fundamental lack of understanding of the way that commercial aircraft are designed, tested, and certified.



Back to the OP.

Thanks for the detailed post.

I still say the proximate cause was a business decision though...

---

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

If you are interested to understand the full scope of the many failures of the 737 max, here you go:
https://spectrum.ieee.org/...a-software-developer

The bottom line, the plane is one kludge on top of another kludge. And, software fix or no software fix, the plane should be scrapped.

---

Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
--

I get what you're saying, and I wouldn't ENTIRELY disagree. We (me and my fellow project engineers... Both in my group and outside it) have spent a good deal of time discussing the systems particulars.

And, it won't surprise me if what you say is the ultimate attibution in this instance. But, have you ever tried to get 50 people to all do the RIGHT THING? There are a lot more people involved in this debacle than THAT. BUT, Even THAT is more frustrating than sometimes seems worth the trouble. People suck.

I guarantee there are 100s of people involved in all the affected systems here. So, turn that around and try to get XXX to commit to doing THE WRONG THING... where no one will blow the whistle...for being "Forced" to shut up and do what they are told. No one is ignorant to (or callous of) the fact that human lives are at stake in this industry. It is lesson number 1-10. We live and breath it.

I work with engineers at Boeing. People who used to work at Boeing work for me, now. Hell, I work with every major airframe manufacturer in the world except airbus---not sure why that is, I've worked with dassault... So it's not a French thing. I have NEVER worked with someone who would consciously compromise aircraft safety for a dollar. Simply never. Further, the people on the certification side are an entirely different breed of ethical.

My point being... It's just more complicate than can be distilled to a simple, single decision. Too many people didn't realize the circumstances they were setting into motion. Every choice along the way seemed right, at the time. Nevertheless, we need a simple villain. So, as I said, it won't surprise me if there is a scapegoat in the news even if the ntsb report is more nuanced.

Ugh. That article is worse (less well informed) than anything written in this thread. I liken it to click bait. I'm not even going to start listing the errors in it. I don't know what that guy's problem is, but he is patently wrong about pretty much everything about how this really happens.

Well, you should definitely alert the IEEE about that, sounds like their publishing standards have gone down the toilet.

But having a bit of heavy metal experience myself, l would definitely be interested to hear your full critique.

---

Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
--

A full critique would be longer than the article.

I don't know what IEEE publishing standards were used in publishing this, but I note the disclaimer at the top of the article...



That's not a damnation by itself... But nevertheless, IEEE has distanced itself from this article for some reason. Maybe IEEE always puts that disclaimer up....but, if so... Exactly what is the prestige of published in IEEE?

Much of the problems with this article are in the presentation of the problems (and solutions) with the 737 max as being unique / novel. Dynamic instability is not new. Further, it presupposes that the flight characteristics of the 737 max are, in fact, danamically unstable. But, the description of the flight characteristic is not correct, nor does it describe dynamically unstable flight.

Fly by wire is not new---to the degree that the 737max could be considered fly-by-wire. MCAS is not new, it was outfitted on the kc-46 for example. MCAS is NOT and anti-stall control system---and was NEVER intended as such. It was intended to mimic the flight control characteristics of the 737NG, so that 737NG certified pilots could directly transfer over the the max. Anti-stall systems work ENTIRELY in a different manner. Again, this was not intended as a safety system, rather just to make it fly like another aircraft. It is clearly imperfect---catastrophically.

Flight critical software development is not new. Flight critical software development is not under control of a software development manager. Review, evaluation, test and certification are roles that are performed by entirely independant entities... Each role is in dependant of the others in LEVEL A. I've written flight critical software, personally... And I've created entire flight critical development procedures for companies that I've worked for. The auther got more wrong than he got right. For reference, the standard that generally governs such development is DO-178. For direct control of flight surfaces that would be Level A--the most stringent. Such development is NOT performed by junior engineers....those kids get to cut their teeth on Level E---"does not apply". Level A is done by the most expert of software engineers. Engineers who DO inherently understand flight dynamics, and control laws. Often they have advanced degrees in flight sciences or aeronautics.

The article presupposes that that "right" aircraft design changes would have been too expensive for Boeing to contemplate. That is to wholly not comprehend the spending power of a giant such as Boeing---or where Boeing makes its real money. It's not just in the metal. As a sometimes partner, and other times rival with Boeing...trust me, they can spend money like very few can.

Finally, DERs and DARs would not be used by most aircraft OEMs including Boeing for a program of this magnitude. The DER/DAR system is typically used by smaller companies that only sparsely do airworthiness related work... Or for smaller projects that the OEM doesn't want to waste its own more precious resources on. Rather, an organization like Boeing or the company I work for has an independent arm called the ODA (organizational design authority). This is not a materially different process, but the fact that the author doesn't know the difference suggests he's mostly talking out of the wrong end.

The anonymous quote towards the end of the article is humorous, in that it is clearly by someone who CLAIMS to have written avionics software. However, they says this was "ten years ago" as if things were wholly different back then. They were not. I wrote my first DO-178, level B software in 1995, 25 years ago. At that time, the standard was on Rev B. I haven't looked up the original publication date of Rev NC. But, it certainly predates my entry into the engineering field.

Note... This is not a point by point exhaustive critique of the article. It's just enough to point out that there are numerous factual errors... And the article is riddled with bias. There are some truths in it, but... It's hard for those outside the industry to tell fact from fiction.

The worry is you have a light crash or pick up your bike and have the handlebars swing around a few times whatever but a few impacts you think nothing of and as the dude in the youtube video points out some light delimitation and cracking that you don't notice. Next thing you know you're sweeping down a mountain at speed braking hard into a bend and your frame front end is compromised... I don't want to be in that position.

I really liked the S5 and probably is a great bike to ride but I agree with the guy on the video a major design flaw in my opinion. Carbon is not designed to be impacted like that.

Thanks Dan for articulating my thoughts. The video editing was so bad – indeed non-existent – that I couldn't make it more than a few minutes through this tedious and repetitive diatribe. I'm surprised that so many viewers have the endurance to make it through the whole "production". Some journalistic integrity would also go a long way to boost confidence, like "I reached out to Cervélo to discuss the issue, and here is their response...".

Raoul . What would you suggest as a bump stop .Consumers demand integration ,aero dynamics stiffness and lightness .Sometimes complete practicality needs to be compromised for ultimate performance . Im suggesting an F1 car would struggle to park in the Maccas car park or if you crash it ,it breaks .

I’m not Raoul, just merely sharing his video. I’m no engineer, and will not pretend to be one. But I was thinking, why not an elongated piece of really hard elastomer clamped onto the steerer tube that will limit the travel as the nose cone tapers to the side.

Usually, the IEEE does not publish clickbait type articles, is your experience otherwise?

But I am puzzled, did you read the article? Because the author does not say dynamic instability is new. He does not say fly by wire is new. He does not say mcas is new. He does not say that mcas is primarily an anti stall system. He does not say that the development of flight software or flight critical software is new. He does not say that the software developent was under the control of a "software development manager" only that the code was created by humans under the direction of managers. He also does not say that such development is performed by junior engineers. He also does not say that aircraft design changes would have been too expensive for Boeing to contemplate, only that designing and certifying a new aircraft takes a lot of money, and that money (and selling points for the airline in saving pilot training costs--also back to money) was the main motivation for not going that route.

Ultimately, the economic decisions to create the frankenstein 737 max have proven to be an enormous disaster, one only needs to look at the dead bodies and boeing's bottom line to see that. And where exactly within boeing the buck stops is a good question. But this massive systems f*ck up will be one that will be studied for decades to come as to how NOT to design an aircraft.

Someone wiser that me once said, "It's more complicated than can be distilled to a simple, single decision. Too many people didn't realize the circumstances they were setting into motion. Every choice along the way seemed right, at the time." I would only add that good design systems are those where people DO realize the circumstances they are setting into motion. And, that in the 737 max case, many of the "choices along the way" were made purely on economic and marketing grounds, and that is where things started heading south fast ...


On a different topic, hope your recovery is progressing well. Hopefully you are finally home and out of the hospital.

---

Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
DarkSpeedWorks.com.....Reviews.....Insta.....Facebook
--

Yes, thanks. Home and exercising (hill walking). Medical parole hearing is Tuesday....for release to work.

I understand the hypothetical concern, but I believe it's just that. Again, where are all the real-world examples of these types of failures if it's that big a design flaw?

He's playing dirty imo. There are compromises and limitations with aero designs. And the original engineering/service could be consulted. We don't know what kind of hit that frame took as well to get to that point.

What's his alternative proposal?

---

Training Tweets: https://twitter.com/Jagersport_com
FM Sports: http://fluidmotionsports.com

He said several times that the previous generation with the replaceable pin was much better.

I’d say they're somewhere around equal given that there is no confirmed cases for either model of this being an issue.

How do you know that? Unless you are in charge of customer service at Cervelo you wouldn’t have access to that info, right? So let’s not make up ‘data’.

hill walking already. that's great. bionic man.

---

Dan Empfield
aka Slowman

He has a couple of examples in his video even marked out where damaged with a marker. As he explained and I explained in my in my post, that it would concern me and what I consider a design flaw as it could happen so easy. I have a Dimond and they have a pin in the base of the fame behind the headset and carbon ridges on the fork in place as stops for over rotation so no structural carbon is impacted. Feel free to buy one, that is your choice but I'll give this model a miss.

Well let’s see, all we have as an example form anyone is this video. If this were an actual problem you think someone who is saying this is poor engineering could come up with someone on the internet that has had this actually happen to them.

So that's assuming and not knowing, and even your guessing doesn't mean a design can not be bad. Sticking your hand in boiling water is a bad idea even though I don't know anyone that's actually done that.

sticking head in the sand seems to be the strategy of some here, tho

But unlike boiling water no one can agree if it is a good or bad idea...